This invention relates to a release mechanism for a riveting or nailing gun comprising an overhead valve.
Compressed air guns for firing metal nails or staples are known at the present time. These nailing guns are constituted generally by a hollow casing or head carrying a pneumatic cylinder in which a striking mass slides in order to cause rapid expulsion of the nails contained in a suitable magazine in the gun. Said striking mass is operated pneumatically by an overhead valve controlled by a trigger release mechanism. This trigger acts generally on the plug of a pilot valve associated with the overhead valve.
Safety reasons require that the pistol can only fire when in contact with the piece to be nailed. This is usually effected by means of a feeler which acts on a lever disposed between the trigger and pilot valve plug or pivoted to the trigger, so that if the lever is not moved by the feeler, the trigger rotates without engagement, and thus without moving the valve plug.
The drawbacks arising with known nailing guns mainly relate firstly to the return to the safety position after any individual shot, and secondly to the ability to carry out shots in succession under so-called repetition operation.
This second requirement is felt in particular by the more expert operators, who are thus able to carry out their work more rapidly.